linux-kernel - [PATCH 3.16 287/294] drbd: avoid redefinition of BITS_PER

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Message-ID: <lsq.1510009382.238789508@decadent.org.uk>
Date:   Mon, 06 Nov 2017 23:03:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Jens Axboe" <axboe@...com>,
        "Arnd Bergmann" <arnd@...db.de>,
        "Lars Ellenberg" <lars.ellenberg@...bit.com>,
        "Philipp Reisner" <philipp.reisner@...bit.com>
Subject: [PATCH 3.16 287/294] drbd: avoid redefinition of BITS_PER_PAGE

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Lars Ellenberg <lars.ellenberg@...bit.com>

commit 2630628b2dbc3fc320aafaf84836119e4e3d62f1 upstream.

Apparently we now implicitly get definitions for BITS_PER_PAGE and
BITS_PER_PAGE_MASK from the pid_namespace.h

Instead of renaming our defines, I chose to define only if not yet
defined, but to double check the value if already defined.

Signed-off-by: Philipp Reisner <philipp.reisner@...bit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@...bit.com>
Signed-off-by: Jens Axboe <axboe@...com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/block/drbd/drbd_bitmap.c | 6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -478,8 +478,14 @@ void drbd_bm_cleanup(struct drbd_device
  * this masks out the remaining bits.
  * Returns the number of bits cleared.
  */
+#ifndef BITS_PER_PAGE
 #define BITS_PER_PAGE		(1UL << (PAGE_SHIFT + 3))
 #define BITS_PER_PAGE_MASK	(BITS_PER_PAGE - 1)
+#else
+# if BITS_PER_PAGE != (1UL << (PAGE_SHIFT + 3))
+#  error "ambiguous BITS_PER_PAGE"
+# endif
+#endif
 #define BITS_PER_LONG_MASK	(BITS_PER_LONG - 1)
 static int bm_clear_surplus(struct drbd_bitmap *b)
 {